Conventionally, negative-type photoresists used for the formation of black matrices and phosphor patterns of color cathode-ray tubes, etc., have made use of resists composed of a water-soluble polymer such as polyvinyl alcohol and a bichromate salt (called PVA-ADC-based resists). Photoresists of this type have a fundamental disadvantage in that they require a special treatment facility for preventing environmental pollution, which is otherwise caused due to the presence of bichromate salts.
As photoresists that are free from the above problem, there have been known photosensitive compositions containing a water-soluble diazide compound, e.g., sodium 4,4'-diazidostilbene-2,2'-disulfonate (hereinafter abbreviated DAS), which serves as a photocrosslinking agent, and a water-soluble polymer that is photocrosslinkable in the presence of the water-soluble diazide compound. For example there are proposed photosensitive compositions containing, as polymer matrices, vinyl alcohol-maleic acid copolymers or salts thereof (Japanese Patent Application Laid-Open (kokai) No. 48-97602), vinyl alcohol-acrylamide copolymers (Japanese Patent Application Laid-Open (kokai) No. 48-97603), or water-soluble polyvinylbutyrals (Japanese Patent Application Laid-Open (kokai) No. 48-98905). In practice, however, these compositions cannot be used because of their low sensitivity. At present, known compositions having sufficient sensitivity in practice include those containing polyvinylpyrrolidone (hereinafter abbreviated PVP) and a water-soluble diazide compound serving as an additive (hereafter, compositions of this type will be referred to as PVP-DAS-based resists; see, for example, Japanese Patent Application Laid-Open (kokai) No. 48-90185), as well as those containing an acrylamide-diacetoneacrylamide copolymer (hereinafter abbreviated PAD) and water-soluble diazide serving as an additive (hereafter, compositions of this type will be referred to as PAD-DAS-based resists; see, for example, Japanese Patent Application Laid-Open (kokai) No. 50-33764).
When used for the formation of black matrices of color cathode-ray tubes, PVA-ADC-based resists have a drawback of poor resolution, in addition to the aforementioned problem of environmental pollution, due to low oxygen permeability and lack of reciprocity-law failure characteristics. In contrast, when PVP-DAS-based resists are used, due to their excessively high oxygen permeability, proper sensitivity cannot be obtained unless the thickness of coating film is increased, which in turn reduces resolution. PAD-DAS-based resists, on the other hand, are endowed with excellent sensitivity and resolution, but after they have undergone formation of resist patterns and coating with graphite they provide poor etching characteristics, and, depending on the type of graphite, etching cannot be effected.
With regard to use for the formation of phosphor patterns, PVA-ADC-based resists are unsatisfactory in terms of both environmental pollution and sensitivity, and in addition, chromium oxide which remains after firing degrades the luminance of the phosphor. In this respect, PVP-DAS-based resists and PAD-DAS-based resists have drawbacks in terms of sensitivity, and therefore cannot be used.
Meanwhile, there are known non-chromium resists which are used for the formation of phosphor patterns and which contain as a photosensitive unit a photosensitive resin obtained through a condensation reaction between unmodified polyvinyl alcohol and a quaternary ammonium salt (e.g., a styrylpyridinium salt or a styrylquinolinium salt) (Japanese Patent Application Laid-Open (kokai) Nos. 55-23163, 55-62905, and 56-11906). However, these resists are also unsatisfactory in terms of resolution.
As described above, there exist no conventional photoresists that simultaneously satisfy requirements with respect to environmental pollution, sensitivity, and resolution. Therefore, there is still need for novel resist materials that exhibit excellent characteristics.
In view of the foregoing, an object of the present invention is to provide photosensitive compositions which do not cause environmental pollution and which exhibit high resolution and satisfactory sensitivity.